In recent years, electrochemical elements, especially lithium secondary batteries have been widely used as power supplies for small-sized electronic devices such as mobile telephones, notebook-size personal computers and the like, power supplies for electric vehicles, as well as for electric power storage, etc. These electronic devices and vehicles may be used in a broad temperature range, for example, at midsummer high temperatures or at frigid low temperatures, and are therefore required to be improved in point of the charging and discharging cycle properties well balanced in a broad temperature range.
A lithium secondary battery is mainly constituted of a positive electrode and a negative electrode containing a material capable of absorbing and releasing lithium, and a nonaqueous electrolytic solution containing a lithium salt and a nonaqueous solvent. For the nonaqueous solvent, used are carbonates such as ethylene carbonate (EC), propylene carbonate (PC), etc.
As the negative electrode, known are metal lithium, and metal compounds (metal elemental substances, oxides, alloys with lithium, etc.) and carbon materials capable of absorbing and releasing lithium. In particular, a lithium secondary battery using a carbon material capable of absorbing and releasing lithium, such as coke, artificial graphite, natural graphite or the like, has been widely put into practical use.
For example, it is known that, in a lithium secondary battery using a highly-crystalline carbon material such as natural graphite, artificial graphite or the like as the negative electrode material therein, the decomposed product or gas generated through reductive decomposition of the solvent in the nonaqueous electrolytic solution on the surface of the negative electrode during charging detracts from the electrochemical reaction favorable for the battery, therefore worsening the cycle properties of the battery. Deposition of the decomposed product of the nonaqueous solvent interferes with smooth absorption and release of lithium by the negative electrode, and therefore, in particular, the low-temperature load characteristics after high-temperature charging storage may be thereby often worsened.
In addition, it is known that a lithium secondary battery using a lithium metal or its alloy, or a metal elemental substance such as tin, silicon or the like or its metal oxide as the negative electrode material therein may have a high initial battery capacity but the battery capacity and the battery performance thereof such as cycle properties greatly worsens, since the micronized powdering of the material is promoted during cycles thereby bringing about accelerated reductive decomposition of the nonaqueous solvent, as compared with the negative electrode of a carbon material. In addition, the micronized powdering of the negative electrode material and the deposition of the decomposed product of the nonaqueous solvent may interfere with smooth absorption and release of lithium by the negative electrode, and therefore, in particular, the low-temperature load characteristics after high-temperature charging storage may be thereby often worsened.
On the other hand, it is known that, in a lithium secondary battery using, for example, LiCoO2, LiMn2O4, LiNiO2, LiFePO4 or the like as the positive electrode, when the nonaqueous solvent in the nonaqueous electrolytic solution is heated at a high temperature in the charged state, the decomposed product or the gas thereby locally generated through partial oxidative decomposition in the interface between the positive electrode material and the nonaqueous electrolytic solution interferes with the electrochemical reaction favorable for the battery, and therefore the low-temperature load characteristics after high-temperature charging storage are thereby also worsened.
As in the above, the decomposed product and the gas generated through decomposition of the nonaqueous electrolytic solution on the positive electrode or the negative electrode may interfere with the movement of lithium ions or may swell the battery, and the battery performance is thereby worsened. Despite the situation, electronic appliances equipped with lithium secondary batteries therein are offering more and more an increasing range of functions and are being in a stream of further increase in power consumption. With that, the capacity of lithium secondary batteries is being much increased, and the space volume for the nonaqueous electrolytic solution in the battery is decreased by increasing the density of the electrode and by reducing the useless space volume in the battery. Accordingly, the situation is that even decomposition of only a small amount of the nonaqueous electrolytic solution may worsen the high-temperature cycle properties and the low-temperature characteristics after high-temperature cycles.
As a lithium primary battery, for example, known is one in which the positive electrode is formed of manganese dioxide or fluorographite and the negative electrode is formed of lithium metal, and the lithium primary battery of the type is widely used as having a high energy density, for which, however, it is desired to prevent the increase in the internal resistance during long-term storage and to improve the long-term storage performance at high temperatures.
Recently, further, as a novel power source for electric vehicles or hybrid electric vehicles, electric storage devices have been developed, for example, an electric double layer capacitor using activated carbon or the like as the electrode from the viewpoint of the output density thereof, and a hybrid capacitor including a combination of the electric storage principle of a lithium ion secondary battery and that of an electric double layer capacitor (an asymmetric capacitor where both the capacity by lithium absorption and release and the electric double layer capacity are utilized) from the viewpoint of both the energy density and the output density thereof; and it is desired to improve the load characteristics after high-temperature charging storage of these capacitors.
Patent Reference 1 discloses an electrolytic solution containing, in a nonaqueous solvent, from 0.1 to 30 parts by weight of a sulfonate compound of which the carbonate skeleton-containing 5-membered ring structure has an oxysulfonyl group at the 4-position thereof via a methylene chain, such as 1,3-dioxan-2-onyl-4-methyl methyl sulfonate (also called 4-(methanesulfonyloxymethyl)-1,3-dioxolan-2-one), saying that the battery containing the electrolytic solution of the type is excellent in cycle properties.
Patent Reference 2 discloses an electrolytic solution containing, in a nonaqueous solvent, from 0.1 to 30 parts by weight of erythritan sulfite of which the sulfite skeleton-containing 5-membered ring structure has an ether oxygen at the 4-position thereof via a methylene chain, saying that the battery containing the electrolytic solution of the type is excellent in cycle properties.